The present invention relates to a belt for a belt drive device, and more particularly to a belt for continuously variable belt-drive transmission for a motor vehicle.
A known continuously variable belt-drive transmission disclosed in U.S. Pat. No. 4,369,675 comprises an endless belt running over a drive pulley and a driven pulley. Each pulley comprises an unmovable conical disc and a movable conical disc which is axially moved by a fluid operated servo device so as to vary the running diameter of the belt on the pulleys in dependency on driving conditions.
The belt comprises a plurality of metal elements arranged adjacent to each other in the longitudinal direction of the belt, and a pair of endless carriers inserted in opposed slits of each element, each carrier comprising a laminated metal ring.
Referring to FIG. 9, the element E has a body portion Bp, the sides S of which abut on conical faces of disks D.sub.1, D.sub.2 with each disk having a slope angle .beta.. A length .alpha. between the uppermost point a.sub.1 and the lowermost point b.sub.1 of contact side S is the same as the length of the side opposite the angle .beta. in a right-angle triangle a.sub.1 a.sub.2 b.sub.1. Namely, the length .alpha. is expressed as .alpha.=Pwsin, .beta., where Pw is a pitch width on a line P'--P' passing through the points a.sub.1 and a.sub.2.
When the element E enters the groove of the pulley at a correct attitude without distortion, as shown by a dotted line, both contact sides S of the body portion Bp appropriately rest on the slopes of the disks D.sub.1, D.sub.2. To the contrary, when the element E is inclined as shown by a solid line the element E touches the disks only at diagonal points a.sub.2 and b.sub.1. In particular, in a low belt tensioning pressure range where the tension of the carrier C is low, the inclined attitude of the element E cannot be corrected so that the element stays slanted while passing around the pulleys.
Accordingly, one of the carriers C is raised by a shoulder Sh of the element E which deviates from the normal position, so that the carrier C is excessively tensioned. As a result, the durability of the carrier C decreases. In addition, the innermost ring of the carrier C is damaged as a result of an abnormal increase in friction between the shoulder Sh and the underside of the innermost ring.
Japanese Patent Application Laid-Open 61-192944 discloses elements to eliminate the abovedescribed disadvantage. The element comprises a pair of support blocks and a compression block supported by the support block and having V-shaped surfaces which abut on the pulleys. However, the shape of the element is complicated.